A section of the Hadrian's Wall at Peel Gap near Once Brewed, England.  This section of the wall is more modern in date.  The original Roman wall starting in 122AD under the rule of Emperor Hadrian & spanned 73 miles from the Irish Sea to the North Sea.  It served as a northern defensive fortification for the Roman province of Britannia until the end of Roman rule in 410AD.  The north side of the wall was also accompanied by a v-shaped trench for defense.  Today, much of the wall has disappeared except for here in the central hilly sector.  Originally 15-20 feet in height, the wall has been much reduced for later stone building or other nearby rock walls.  Pennine Way, a 268-mile long national trail in the UK, follows alongside the wall.

More info here: https://en.wikipedia.org/wiki/Hadrian%27s_Wall